fix pullrequests/invert_binary_tree

Author: rihib

pullrequests/invert_binary_tree/step3.go

@@ -0,0 +1,10 @@
+//lint:file-ignore U1000 Ignore all unused code
+package invertbinarytree
+
+func invertTreeRecursive(root *TreeNode) *TreeNode {
+	if root == nil {
+		return nil
+	}
+	root.Left, root.Right = invertTreeRecursive(root.Right), invertTreeRecursive(root.Left)
+	return root
+}